1. Field of the Invention
This invention relates generally to ceiling jacks and more particularly to ceiling jacks that may be easily adjusted by one operator.
2. Description of the Prior Art
One prior art device used for supporting ceiling material while such material was being nailed to ceiling beams describes a hand crank used to raise a platform or table upon which the ceiling tile or other material rested while being elevated into place. A cable and drum arrangement was utilized to effect vertical extension of telescoping tubular members. A pawl and ratchet arrangement was provided to maintain the required position once it was reached. Among the drawbacks of this prior art device are its complexity and its necessary cumbersomeness. It is also to be noted that its efficient operation required the presence of at least two workmen. Damage to the surface of the ceiling material often resulted due to the unsatisfactory performance of the adjusting mechanism of the device. The device was not continuously adjustable, rather, it was adjustable only to the positions defined by the pawl and ratchet mechanism.
Another prior art device provided an interconnecting group of jacks. This device is cumbersome and complex and adjustment, being effected by a ratchet arrangement, is discrete rather than continuous and therefore, less than satisfactory. In these prior art devices, even where it is possible for one operator to perform the required adjustments, the operator, if he is on a ladder, scaffold or other device placing him close to the site of the attachment of the ceiling material, must dismount and return to floor level to perform these adjustments. Upon returning to the site of attachment, i.e., the ceiling, experience teaches that often additional adjustments must be made necessitating yet another return to floor level. Such a procedure can become tedious, time consuming and therefore, expensive.
It would be of great value to the art to provide an elevator and support device, continuously adjustable from the operator's position on a ladder or scaffold where the operator might be immediately aware of the result of trial adjustments made and therefore, might correct for such adjustments without disturbing his position. It would be of additional great value if such a device could be made simple in design and construction, inexpensive to manufacture and conveniently portable.